For decades, the email ecosystem has operated on a fundamental imbalance of power. Mailbox providers—the gatekeepers of the inbox—have maintained strict control over the reputation systems that determine whether a message reaches a user or vanishes into the void of a spam folder. Senders, meanwhile, have been forced to rely on "black box" diagnostics, reverse-engineering their performance based on fluctuations in open rates or bounce codes.
That era of opacity may be drawing to a close. A new proposal currently working its way through the Internet Engineering Task Force (IETF), known as the Aggregate Performance Reporting Format (APRF), promises to provide senders with the granular, machine-readable data they have craved since the dawn of commercial email.
The Genesis of APRF: A Collaborative Breakthrough
The landscape of email deliverability changed on March 17, 2026, with the publication of draft-brotman-aggregate-performance-reporting-00. The document, while still in its infancy, represents a historic alignment of interests.
The author list itself is a signal of the industry’s changing tide: Alex Brotman, Senior Engineer for Anti-Abuse at Comcast; Tom Corbett of Iterable; and Emil Gustafsson of Google. When a major mailbox provider (Comcast), a prominent Email Service Provider (ESP), and the world’s largest consumer mailbox provider (Google) collaborate on a standards-track document, the industry pays attention.
The proposal is the direct result of a long-standing frustration: the "guesswork" inherent in modern email marketing. While tools like Google Postmaster Tools and Microsoft’s SNDS have provided glimpses into reputation, they are proprietary, siloed, and often difficult to integrate into automated sender infrastructure. APRF seeks to unify these insights into a standardized, open-source protocol.
Chronology: From Concept to Production Code
The journey toward APRF did not begin in a boardroom, but in the practical, daily grind of anti-abuse engineering.
- Early 2026 (Pre-March): Alex Brotman began developing internal telemetry for Comcast. Recognizing the limitations of existing proprietary feedback loops, he authored a technical framework designed to share aggregate performance data directly with senders.
- March 17, 2026: The IETF officially published
draft-brotman-aggregate-performance-reporting-00. The release was accompanied by a candid social media announcement from Brotman, confirming that "running code" was already live in production at Comcast, providing aggregate reports for domain-authenticated senders. - Post-March 2026: The industry entered a phase of peer review. As of now, the draft is being socialized within technical circles, with the expectation that it will eventually be adopted by an IETF working group—most likely the MAILMAINT group—to formalize the standard.
Brotman’s decision to launch with working code rather than a theoretical white paper was a strategic choice. By proving the viability of the protocol in a live environment, he has invited the community to refine the implementation before it becomes a rigid, international standard.
Technical Foundations: How APRF Works
If DMARC (Domain-based Message Authentication, Reporting, and Conformance) is the gold standard for verifying identity, APRF is designed to be the gold standard for verifying impact.
Discovery and DNS
APRF leverages the existing DNS infrastructure. When a mailbox provider identifies a message as originating from a domain with a valid DKIM (DomainKeys Identified Mail) signature, it initiates a DNS lookup for a specific TXT record: <selector>._aprf._domainkey.<your domain>. This record contains the configuration for where and how the sender wants to receive their performance reports, mirroring the rua (Reporting URI for aggregate data) mechanism used in DMARC.
The Payload: JSON and SMTP
Reports are delivered as machine-readable JSON files, transmitted as attachments via multipart/report SMTP messages. By utilizing gzip compression, the format ensures that even high-volume senders can process vast amounts of data without overwhelming their internal storage or ingestion pipelines.
The SDI (Signer-Defined Identifier)
One of the most innovative features of the APRF proposal is the sdi attribute. This allows senders to nominate a specific DKIM-signed header to segment their own data. Whether a sender wants to track performance by geographic region, specific brand identity, or individual marketing campaign, the sdi attribute enables a level of visibility that was previously impossible without relying on proprietary, platform-specific analytics.
Implications for the Email Industry
The potential shift in the power dynamic between senders and receivers cannot be overstated. If widely adopted, APRF would transform deliverability from a reactive practice to a proactive science.
1. The Death of the "Black Box"
For years, deliverability consultants have acted as interpreters of the "tea leaves"—guessing why a sudden dip in inbox placement occurred. APRF replaces this speculation with hard, standardized metrics. By knowing exactly where mail is being placed and how users are engaging with it on a domain-by-domain basis, senders can troubleshoot technical issues in minutes rather than weeks.
2. Standardized Ecosystems
The fragmentation of reporting tools is a significant burden for enterprise senders. A sender using five different mailbox providers must currently manage five different dashboards. APRF creates a single, unified format that can be ingested by a single centralized dashboard. This lowers the barrier to entry for smaller senders and allows larger enterprises to build better, more efficient internal monitoring tools.
3. The Google Factor
The inclusion of a Google engineer as a co-author is the "elephant in the room" that everyone is watching. While Google has made no formal promise to implement APRF across Gmail’s massive infrastructure, their participation in the drafting process suggests a willingness to modernize how they communicate with the sender community. If Google were to adopt the standard, it would effectively set the global benchmark for email hygiene and deliverability.
Reality Check: The Road Ahead
Despite the excitement, the industry must maintain a sense of perspective. As Brotman himself noted, the current draft is -00—it is a starting point, not a finished product.
- It is not a guarantee of placement: Even with perfect data, there is no "golden ticket" to the inbox. APRF provides the diagnostic data, but the sender is still responsible for maintaining high-quality mailing practices.
- The standard is in flux: The draft currently contains unresolved technical questions, including how to manage data overlaps and the ABNF (Augmented Backus-Naur Form) syntax, which is still being finalized.
- Voluntary participation: APRF is not a mandate. It relies on the voluntary cooperation of mailbox providers. While the benefits of reduced support tickets and improved sender quality provide a strong incentive for providers to adopt it, it will likely be a phased, multi-year rollout.
Conclusion: A Call to Action
The window for shaping the future of email deliverability is open. The IETF process relies on community input to stress-test ideas, identify edge cases, and ensure that the final specification is robust enough for global adoption.
For infrastructure engineers, ESPs, and large-scale senders, the imperative is clear: engage with the draft. Review the technical specifications on the IETF Datatracker, participate in the mailing lists, and provide feedback to the authors.
We are currently witnessing the birth of a protocol that could do for email performance what DMARC did for email security. By moving toward a transparent, data-driven relationship between senders and mailbox providers, the entire ecosystem stands to benefit. The black box is finally opening; it is up to the industry to decide what happens next.
